Although women can expect to live one half of their adult lives beyond menopause, knowledge about this physiologic event and its various influences on subsequent health and quality of life remains incomplete. In Massachusetts we studied a population-based random sample of 7828 white women, aged 45 to 55 years (response rate, 77%). The median age at last menstruation for the sample is 51.4 +/- 0.19 (SE) years years, and we found no evidence of a secular trend towards a later age at menopause in the last 25 years. Current smokers reach menopause an average of 1.74 years earlier than nonsmokers (t = 3.78, p less than 0.01), but the quantity smoked has a negligible effect. Other potential correlates measured--education and marital status, number of children, and urban/rural residence--have little effect on the age at menopause. The results confirm earlier, more tentative findings from clinical populations.